Mold operation controls

Mold Coolers for Plastic Injection Molding. Heat pipes are used for local temperature control in the injection molding of plastics (see Polymerprocessing). A heat pipe is often used to force local cooling within a mold to speed operation, control viscosity, retention of material in a difficult mold area, or to reduce thermal stresses on cooling. 

The process provides fast molding cycles, unlimited shelf life for the sheet, large part capability, and design flexibility. The process also allows for scrap materials to be recycled. Trim waste from the molding operation and defective parts can be ground up and recycled into the basic sheet process in controlled amounts. Some of this waste has also been used as input for injection molding. 

Many problems in manufacturing of final products by blow molding are controlled by proper selection of parameters under which machinery is operated (not a subject of this book) but some can also be remediated by formulation change, for example ... 

From these controlled test results, and also from real world molding operations where silica has been used in commercial fluorescent color concentrates, it is quite apparent that processing problems associated with plateout can be dramatically reduced by the addition of a silica product (either fumed or precipitated). Also, the use of silica will help in the dispersion of fluorescent color (i.e., less streaking) and in minimizing the appearance of the weld line on blow molded bottles. 

An industry-standard programmable logic control has been added to a RTM valve, which allows a single pump to feed ten stations and can give remote flushing without removing the gun from the mold. The control works in concert with the computer-controlled process monitor, operated by remote keypad and, in combination, greatly improves and facilitates the RTM process. 

Ultimately, the reciprocating screw system was developed. Adaptation of such units led to improved rates of softening or melting of the plastic, closer tolerances on short size (amount of plastic to mold), better control of temperatures and more reliable overall performance. They are also highly effective for vented operation. 

---